A conveyor is frequently used to move signatures between a number of operating stations. Signatures typically comprise one or more pages which are formed into books, such as catalogs, magazines, pamphlets, etc. The operating stations, which are supplied with signatures by the conveyor, perform selected operations upon those signatures, including collating, trimming, binding and the like.
One known conveyor for conveying signatures to various operating stations includes a continuous chain which is propelled by one or more motor driven sprockets. In the past these continuous chains have been comparatively short needing to be only long enough to accommodate 8 to 10 signature insertion points. In such a system it was necessary to occasionally increase chain tension to take up slack which could cause the chain to jump sprocket teeth and thereby lose timing of the system.
More recently these continuous chains and conveyor systems have reached lengths that are up to three times longer than in the past. As a result the tension applied to maintain the chain timing has also tripled and the necessity to increase the tension occurs much more often with the resulting increase in chain wear, chain stretch and eventually chain replacement. Proper tensioning of an endless conveyor during operation is an important consideration for smooth and efficient operation as well as minimizing wear. Slack in the conveyor is not desirable since it results in erratic movement and undue wear, while too much tension in the chain also results in excessive wear (due to strain and over/stressing) as well as "chain stretch" which is a lengthening of a chain due to tensile forces and/or wear applied over time.